This is pretty cute actually. I like how visibly gentle Chisato is, sipping daintily, making sure there's not much blood spilling out of the wound, or that the bite isn't too deep or painful. She may be a vampire, but she's still Chisato, so she'd rather not cause any major harm to anyone she bites, much less to Takina. I can even imagine her patching her up afterwards, and finishing it all off with a warm hug, in typical Chisato fashion.
Am I a sucker (pun not intended) for Chisato being portrayed as a tender, affectionate and gentle, albeit clingy girlfriend? Eeeeeeeehehehehehehe yes.